It is either lichen urticatus or prurigo simplex
There may be some cause.
It may be insects,allergy or some irritant..or some internal cause.
It may be psychological cause..anxiety and depression
Thorough clinical history, keen examination and investigations may be done by expert to diagnose the condition.
For that, you consult dermatologist
in tappering dose and anxiolytic drugs may be taken to improve the condition under guidance of dermatologist.
If there found some cause, take care of it..
Avoid soap bath.
Take good sleep.
I think you might be alright.
I hope you got my answer.
Dr. Ilyas Patel MD